Conventional load weight measuring systems of the kind specified to be mounted on construction machines are disclosed in pre-publications of Japanese Laid-open Patent Applications NOS. SHO 58-6422, SHO 59-9520, SHO 59-70919, SHO 59-75123, SHO 59-84118, SHO 59-84119, SHO 60-80721 and SHO 58-162816, and Japanese Laid-open Utility Model Application No. SHO 59-38576, etc.
These load weight measuring systems, which have already been disclosed, comprise a weight indicating unit and a printer unit.
The weight indicating unit serves to indicate the weight of one scoop of load by a bucket, and the weight of the load scooped by the bucket a number of times (or the cumulative weight of the load).
Therefore, it is satisfactory to find a half day or one day work volume. Whilst, when a dump truck is to be laden with a prescribed quantity of load, it is necessary to take on the load, for example, three or four times. However, to estimate the weight of the load to be scooped by the bucket at the final time, it is required for the operator or the driver to subtract the current indicated weight from the prescribed weight of the load in mental arithmetic. This method is troublesome and is liable to cause a miscalculation, and has posed a problem that because of overloading it becomes necessary in some cases to load the dump truck again, resulting in a waste of much labour and time.